The present invention relates to a magnetic disk recording apparatus, and more particularly, to a circuit for controlling the write current applied to magnetic heads (i.e., data transducers) to write data on magnetic disks of the magnetic disk recording apparatus.
A magnetic disk recording apparatus, such as a hard disk drive (HDD) or a floppy disk drive (FDD), is generally used as an auxiliary memory device for a computer system. A hard disk drive (HDD) usually has the capacity to stably store a large amount of data, and enables rapid access to stored data. As the writing density of magnetic disks for hard disk drives (HDDs) is continuously increased in order to increase data storage capacity, the magnetic heads must operate with a high degree of precision and therefore be very sensitive to a write current. Accordingly, the magnitude of the write current applied to the magnetic heads is a critical factor in the performance of the hard disk drive (HDD). For example, an increase in the magnitude of the write current causes an increase in the amplitudes of signals picked up by the magnetic heads when reading data from the disks.
Several references discuss the subject of write currents in a magnetic disk recording apparatus. U.S. Pat. No. 5,550,774 entitled Current Setting Circuit To Provide A Write Current To A Recording Apparatus issued to Watanabe et al is one such reference. In Watanabe et al. ""774, a write current setting circuit for a magnetic recording apparatus employs a reduced number of integrated circuit (IC) pins by enabling an increase of the integrated circuit (IC) pins accompanying an increase in the number of modes to be kept to a minimum. According to these principles, when six external resistance elements are used to generate a sub-mode correction current, (2xc3x97n) modes can be set by (n+1) pins of the integrated circuit. While this type of conventional art provides merit in its own right, I note that it fails to address specific problems that plague the art. For example, I note that it fails to recognize that the amount of write current employed should be varied for each of the different magnetic heads and disks of a hard disk drive (HDD).
It is an object of the present invention to provide a write current control circuit and method capable of reducing errors when reading and writing data in a magnetic disk recording apparatus.
It is another object to provide a write current control circuit and method that can adaptively control the write current employed in a magnetic disk recording apparatus.
It is still another object to provide a write current control circuit and method for a magnetic disk recording apparatus that adjusts the write current to an optimum state without modifying the hardware structure of the magnetic disk recording apparatus.
It is yet another object to provide a write current optimizing method for automatically controlling the write current so that the write current is in an optimum state for each of the heads and disks of a magnetic disk recording apparatus.
To achieve these and other objects, the present invention provides a circuit for controlling a write current employed in a magnetic disk recording apparatus. The circuit includes a write unit for delivering the write current to a plurality of magnetic heads to enable writing of data on surfaces of magnetic disks by the magnetic heads. The write current exhibits a first magnitude that varies in dependence upon a second magnitude exhibited by a driving current provided to a write current control terminal of the write unit. A control unit generates pulse width modulated signals having duty cycles corresponding to respective predetermined write current control values to indicate the write current. A write current adjusting unit receives the pulse width modulated signals and delivers the driving current to the write current control terminal of the write unit. The write current adjusting unit adjusts the second magnitude exhibited by the driving current in dependence upon the duty cycles of the pulse width modulated signals. The write current adjusting unit smoothes the pulse width modulated signals, and generates corresponding direct current voltage levels to adjust the second magnitude exhibited by the driving current.
These and other objects can also be achieved in accordance with the principles of the present invention with a method for optimizing a write current employed in a magnetic disk recording apparatus. In the method, a predetermined number of read tests are performed and a number of data errors generated during each one of the read tests is detected. Each one of the read tests is performed for a corresponding one of a plurality of different write current control values, and each one of the write current control values represents a different magnitude of the write current. An optimum write current control value is defined based on one or more of the write current control values corresponding to a minimum number of the data errors.